1. Field of Invention
This invention relates to antennas. Specifically, the present invention relates to antennas used for mobile communication and Global Positioning System applications.
2. Description of the Related Art
Currently, there is an ongoing need to add additional features to mobile telephones equipped with high and low band transceivers, e.g., U.S. Cellular, Japan Cellular, Korean PCS, U.S. PCS, NMT, IMT2000 etc. One feature currently under consideration relates to position location. That is, in response to U.S. Government mandates relating to the provision of emergency services, the cellular telephone industry is currently looking into a variety of systems and techniques for ascertaining the position of a user of a cellular telephone. In fact, cellular and PCS service providers around the world are considering position location technology as a future enhancement. One very promising approach involves a use of the Global Positioning System (GPS).
The GPS system consists of a constellation of low earth orbiting satellites that transmit signals in accordance with a highly accurate onboard clock. Signals received from four satellites by a receiver located on or near the surface of the earth are triangulated to provide a fix on location of the receiver.
While current proposals involve an integration of the GPS receiver into the electronic circuitry of a cellular phone, current designs call for the use of separate antennas for the cellular communications and GPS position location subsystems thereof.
For numerous reasons, e.g. size, cost, weight, and consumer appeal, there is a need for a system or method for using a single antenna to effect communication to and from two or more separate transmitters or receivers in a mobile telephone or other system with a small form factor.
The need in the art is addressed by the antenna sharing system and method of the present invention. In the illustrative embodiment, the inventive system is adapted for use with an antenna and includes a first matching network coupled to a first circuit; a second matching network coupled to a second circuit; and a switch having a first throw coupled to the first network, a second throw coupled to the second network, and a pole coupled to the antenna.
In the specific implementation, the first circuit is a mobile subsystem and the second circuit is a Global Positioning System subsystem. The system further includes a controller for selectively actuating the switch whereby the first network is coupled to the antenna in a first operational mode and the second network is coupled to the antenna in a second operational mode.
In the illustrative implementation, the first network provides an impedance match to the switch and the antenna with respect to the first circuit. The second network provides an impedance match to the switch and the antenna with respect to the second circuit. The first network includes a first inductor (L1) connected between the first circuit and ground, a second inductor (L2) connected between the first throw and ground and a capacitor (C1) between the first throw and the first circuit. The second network includes a first inductor (L3) connected between the second throw and ground and a second inductor (L4) connected between the second throw and the second circuit.